The invention relates to a method and a measuring system for characterizing a deviation of an actual dimension of a component from a nominal dimension of the component.
These types of methods and measuring systems are already known from the prior art and are used to check geometrical and positional tolerances of components. In this case, every component has an ideal geometric shape defined by the nominal dimension, which can be identified by a corresponding description, for example in a drawing or a computer model. However, because of unavoidable manufacturing tolerances in the creation of the concrete component, this ideal shape cannot normally be achieved or at least not for the entire component. As a result, it is important to be able to characterize the deviation of an actual dimension from a nominal dimension of the component sufficiently precisely in order to rework or discard the component, as the case may be.
What must be considered disadvantageous in known methods and measuring systems for characterizing this deviation is the fact that these methods and measuring systems are not suitable for evaluating components with complex geometries. As a result, the object of the present invention is creating a method as well as a measuring system of the type cited at the outset by means of which even deviations of the actual dimension can be characterized in components with complex geometries.
An embodiment of the inventive method, by means of which a deviation of an actual dimension can be characterized from a nominal dimension even in the case of a component having complex geometry, comprises at least the following steps: a) determining at least one measured value characterizing the actual dimension at a position of the component by means of a measuring device; b) making a nominal value available, by means of which the nominal dimension is characterized as a function of the position of the measured value; c) determining a spatial distance between the measured value and the nominal value; d) making a limiting criterion available, by means of which a permissible deviation from the nominal value is characterized as a function of the position of the measured value; and e) determining a tolerance utilization value characterizing the deviation for the measured value as a function of the spatial distance and of the limiting criterion. Therefore, in contrast to the prior art, the inventive method permits a location-dependent standardization and thus a homogenization of previously non-homogenous deviations or by tolerance bands spanned by the limiting criterion. The measured value and the nominal value are preferably determined or made available in this case as spatial coordinates. In this way, for example, even angular tolerances, in which the spatial distance between the measured value and the nominal value increases with an increasing distance from the common point of origin of the rays enclosing the angle, can be determined and reliably characterized. An analogous situation applies to components with convex or concave outer contours, bore holes, or the like.
An advantageous embodiment provides that the steps a) through e) are performed multiple times and/or at several positions of the component. This makes a further improvement in the precision of the characterization possible, because a plurality of measured values is taken into account, and the measuring accuracy is therefore improved. In this case, it can be provided that the deviation of the actual dimension from the nominal dimension of the component be characterized multiple times at one position in order to minimize potential measuring errors. Alternatively or additionally, the characterization can also be carried out at several positions of the component so that the deviations can be characterized over a partial area or surface area of the component. This permits an especially reliable decision to be made about whether the component must be reprocessed or discarded.
Additional advantages are yielded by an upper and/or a lower limit value being used as the limiting criterion. Through this the deviation of the actual dimension from the nominal dimension of the component can be characterized precisely as to whether the measured value lies above or below the nominal value. This supplies valuable information about any reprocessing steps that might be required.
In this case, it has been shown to be advantageous as a function of the concrete geometric design of the component if the upper and the lower limit values are selected with the same and/or a different spatial distance from the nominal value. This facilitates a spatially resolved and optimum definition of a tolerance band that can be adapted to the respective geometry of the component or to its intended purpose.
A further embodiment of the invention provides that the spatial distance in step c) is determined on the basis of a perpendicular and/or a height intersecting line on the nominal dimension at the position of the component. In this way, the respectively most suitable reference plane can be flexibly selected for the tolerance utilization value while taking optimum consideration of the geometric design of the component into account.
A further advantageous embodiment of the invention provides that a color value assigned to the specific tolerance utilization value determined in step e) is displayed by means of an optical display unit. On the basis of the location-dependent standardization of the deviation performed with the aid of the invention, it is possible to quickly and simply recognize on the basis of the assigned color value how strongly the permissible deviation at the affected position of the component was utilized or whether the respective measured value and thus the actual dimension lies above or below the maximum permissible deviation. If several measured values are determined at several positions of the component, surface areas of the component that can be derived therefrom can moreover be colorized depending upon tolerance utilization. The invention makes it possible for measured values with the same tolerance utilization to be assigned to the same color value, even tough the absolute distance between the individual measured values and nominal values is different. This facilitates especially quick classification and evaluation of components with complex geometries so that, for example, angular deviations in funnels or bore holes as well as deviations in the case of components such as engine blades of gas turbines can be characterized without any difficulty.
In this connection, it has been shown to be advantageous in another embodiment that the color value is assigned to the tolerance utilization value on the basis of a variable system of values and/or on the basis of predetermined fixed values and/or symmetrically. An assignment on the basis of a variable system of values makes it possible for example to take different areas of the component and thus different limiting criteria into consideration in an especially simple way. In the case of an assignment on the basis of predetermined fixed values, it can be provided that tolerance utilization values, which do not meet the limiting criterion, be provided with the same color value regardless of the concrete value of the spatial distance between the measured value and the nominal value. In contrast, tolerance utilization values, in which the deviation of the actual dimension from the nominal dimension lies within permissible deviation defined by the limiting criterion, can be assigned a different color value as a function of the respective spatial distance. In this case, for example, a color spectrum corresponding to the size of the distance can be used so that, for example, the brightness of the color value permits a conclusion to be drawn about the utilization of the tolerance band. In the case of a symmetrical assignment of the color value, on the other hand, tolerance utilization values whose measured values have the same (in terms of amount) location-dependent, standardized distance from the nominal value, e.g., ±30% or belong to the same utilization class, e.g., within the permissible deviation or outside of the permissible deviation from nominal value, receive the same color value.
Additional advantages are produced in this case by the range of the several measured values determined in step a) being used as the variable system of values. Thus, for example, a first color value can be determined via the smallest measured value determined with respect to its distance from the standard value, and a second color value can be determined via the greatest measured value determined with respect to its distance from the standard value, between which then a color spectrum is distributed. This makes an especially simple and quick evaluation of the deviations of the component possible independent of whether of the actual dimension has a positive or negative deviation from the nominal dimension.
Additional advantages are produced in that the component is a turbine component, in particular a gas turbine. In connection with the inventively improved characterization of deviations of the actual dimension, it is possible to make an especially quick, cost-effective and reliable assessment of the quality of this component class, which, on the one hand, has complex geometries and in which, on the other hand, adherence to dimensional accuracy is of special importance.
A further aspect of the invention relates to a measuring system for characterizing a deviation of an actual dimension of a component from a nominal dimension of the component, wherein the measuring system comprises a measuring device for determining at least one measured value characterizing the actual dimension at a position of the component; a storage device, by means of which a nominal value and a limiting criterion are made available, wherein, by means of the nominal value, the nominal dimension can be characterized as a function of the position of the measured value and, by means of the limiting criterion, a permissible deviation from the nominal value can be characterized as a function of the measured value; a detecting device for detecting a spatial distance between the measured value and the nominal value; and a determining device for determining a tolerance utilization value characterizing the deviation for the measured value as a function of the spatial distance and of the limiting criterion. In contrast to the prior art, the inventive measuring system makes it possible to standardize the deviation of the actual dimension in a location-dependent way so that even components with complex geometries can be evaluated quickly, simply and reliably with regard to their dimensionally accuracy. The embodiments and further developments presented in connection with the inventive method as well as their advantages apply corresponding to the inventive measuring system.
It has proved to be advantageous in another embodiment that the measuring device be embodied as an optical and/or acoustic and/or mechanical measuring device. This makes possible a particularly exact determination of the measured value and thus a correspondingly reliable characterization of the deviation of the actual dimension at the respective position of the component. The measuring device in this case may be comprised, for example, of a computer tomograph, a laser, an ultrasound transceiver, a caliper gauge, profile gauge, or the like.
Another advantageous embodiment of the invention provides that the detecting device and/or the determining device and/or the storage device is/are a part of a data processing system. This permits quick, simple and cost-effective processing of even larger amounts of data, thereby further improving the characterization of the deviation of the actual dimension. In addition, the measuring system can be embodied in this way to be portable and therefore be used in an especially flexible manner. The measured values or nominal values can be made available in this way as a so-called CAD model of the actual geometry or target geometry of the component.
An especially quick and simple assessment of the characterized deviation is made possible in a further embodiment in that the measuring system comprises an optical display unit, by means of which a color value assigned to the tolerance utilization value can be displayed. The display unit in this case may comprise a monitor, a stereoscopic display, a printer, or the like.
Additional advantages, features and details of the invention are disclosed on the basis of the following description of exemplary embodiments as well as on the basis of the drawings, in which the same or functionally equivalent elements are provided with identical reference numbers.